Military and commercial aircraft utilize numerous engineered systems to control the temperature of heat sensitive components within the aircraft. These systems are designed to transfer heat from components or structures to air, fuel, or water based cooling media through heat exchangers. Operation of these systems degrades airplane performance through a combination of additional aerodynamic drag, parasitic losses, or increased weight. The use of aircraft fuel as a cooling media is the most efficient option as the rejected heat increases the enthalpy of the fuel which in turn has the potential to provide additional energy that can be thermodynamically recovered in the engine cycle.
However, the use of aircraft fuel as a heat sink has not found widespread acceptance in commercial aircraft systems due to a variety of factors. A significant challenge to implementation of fuel-based thermal management systems on aircraft has been and continues to be the formation varnish or coke deposits on high temperature surfaces with which the fuel comes in contact. These deposits can cause problems, such as preventing proper operation of components, clogging passages, or increasing friction between moving parts. One of the factors thought to contribute to coke deposits on high-temperature surfaces is dissolved oxygen content in the fuel. Various systems have been proposed for treating fuel to remove or reduce dissolved oxygen, but these systems also suffer from a number of challenges that have impeded their implementation, including but not limited to cost, energy consumption, payload weight, maintenance issues, and the need to regenerate and/or replenish consumable materials that some of these systems use. Accordingly, there remains a need in the art for alternative systems and techniques for onboard thermal management of aircraft fuel.